1. Field of the Invention
The present invention relates to a communication control apparatus for controlling incoming and outgoing telephone calls in a corporate network and between a plurality of corporate networks by using the IP (Internet Protocol).
2. Description of Related Art
Corporate communication infrastructures are being integrated based on the Internet Protocol, outsourcing of corporate equipment is becoming more and more common, and the VOIP (Voice over Internet Protocol) is gaining power. As a result, a great deal of attention is being paid to IP centrex services, services by which corporate private networks are outsourced to telecommunications carriers.
For example, a non-patent document 1 (Nikkei Communication, Aug. 11, 2003, No. 396, pp. 76-85) describes a mechanism for IP centrex services, in which an IP centrex server provides services for telephone calls such as internal calls and external calls via a corporate VPN (Virtual Private Network) built in wide Ethernet services (Ethernet is a trademark) and IP-VPN services.
Another non-patent document 2 (Nikkei Communication, Aug. 25, 2003, No. 397, pp. 82-83) discloses an example of an IP centrex telephone network with a call control server installed at only one point such as a central point in a corporate network, for controlling incoming and outgoing telephone calls among business hubs.